This invention relates to a method of operating a boiler with gases produced from a bioreactor for anaerobic treatment.
In general, combustible digestion gases are produced from a bioreactor for anaerobic treatment owing to decomposition of organic substances. A calorific value of the gases with a bioreactor having a capacity of 50 m.sup.3 attends as much as 3,600,000 Kcal per day which corresponds to that of approximately 400 liters of heavy oil. On the other hand, this kind of bioreactor usually requires to be heated so that the bioreactor is heated by hot water obtained when the boiler is operated by the produced gases above described.
With such a system, a calorific value of the produced gases under designed loaded conditions is generally more than that required for heating the bioreactor so that the system is constructed to supply the excessive heat as hot water to outside of the system. If an actual load is less than the designed load, the calorific value of the produced gases often becomes insufficient. With the system of the prior art, however, the system would continue supplying the hot water to the outside so that a large amount of heat must be supplied to the bioreactor from an external heat source with steam or the like. Therefore, it is disadvantageous in the viewpoint of effective use of the entire heat.